DBMS MCQs with Answers and Explanations

Question #181

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In a Relational Database Management System (RDBMS), data is logically organized and stored in which form?

A. Graphs

B. Flat text files

C. Tables

D. Trees

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Correct Answer: Option C

Explanation:
In an RDBMS, data is organized into relations, which are logically represented as two-dimensional tables consisting of rows and columns.

This question belongs to: Computer Database Management System (DBMS)

Question #182

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What is the alternative mathematical term used for a 'Table' in a relational database model?

A. Attribute

B. Tuple

C. Relation

D. Domain

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Correct Answer: Option C

Explanation:
In relational model terminology introduced by E.F. Codd, a table is formally referred to as a relation.

This question belongs to: Computer Database Management System (DBMS)

Question #183

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In relational database terminology, a row in a table is precisely called a what?

A. Attribute

B. Tuple

C. Field

D. Relation

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Correct Answer: Option B

Explanation:
A single row or record in a relational database table is formally called a tuple.

This question belongs to: Computer Database Management System (DBMS)

Question #184

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What is a column in a relational database table formally called?

A. Tuple

B. Attribute

C. Entity

D. Degree

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Correct Answer: Option B

Explanation:
A column in a database table represents a property or characteristic of the entity and is formally known as an attribute.

This question belongs to: Computer Database Management System (DBMS)

Question #185

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The total number of attributes (columns) present in a relation determines its what?

A. Degree

B. Domain

C. Schema

D. Cardinality

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Correct Answer: Option A

Explanation:
The number of attributes or columns in a relation is defined as the degree of that relation.

This question belongs to: Computer Database Management System (DBMS)

Question #186

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The total number of tuples (rows) contained within a relational database table is called its what?

A. Cardinality

B. Density

C. Dimension

D. Degree

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Correct Answer: Option A

Explanation:
The number of tuples or rows in a relation is defined as the cardinality of that relation.

This question belongs to: Computer Database Management System (DBMS)

Question #187

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Which of the following SQL commands belongs to the Data Definition Language (DDL) category?

A. UPDATE

B. CREATE

C. INSERT

D. SELECT

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Correct Answer: Option B

Explanation:
The CREATE command is a DDL statement because it defines, modifies, or creates database structures like tables, schemas, or indexes.

This question belongs to: Computer Database Management System (DBMS)

Question #188

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Which SQL command is used to permanently remove an entire table structure along with all its data from the database?

A. REMOVE

B. DELETE

C. DROP

D. TRUNCATE

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Correct Answer: Option C

Explanation:
The DROP command is a DDL statement that completely removes a table's structure, definition, and all its associated data from the database.

This question belongs to: Computer Database Management System (DBMS)

Question #189

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Which of the following commands is used to modify the structure of an existing table, such as adding or deleting a column?

A. MODIFY

B. CHANGE

C. ALTER

D. UPDATE

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Correct Answer: Option C

Explanation:
The ALTER command is part of DDL and is used to modify the schema or structural definition of an existing database object like a table.

This question belongs to: Computer Database Management System (DBMS)

Question #190

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Which SQL command is used to add new rows of data into an existing table?

A. INSERT

B. UPDATE

C. ADD

D. APPEND

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Correct Answer: Option A

Explanation:
The INSERT command is a Data Manipulation Language (DML) statement used to add new records/rows to a table.

This question belongs to: Computer Database Management System (DBMS)

Question #191

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Which clause is used in SQL queries to filter rows and retrieve only those records that satisfy a specific condition?

A. HAVING

B. WHERE

C. GROUP BY

D. ORDER BY

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Correct Answer: Option B

Explanation:
The WHERE clause is used to filter records based on a specified condition before any grouping takes place.

This question belongs to: Computer Database Management System (DBMS)

Question #192

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What type of key uniquely identifies each record in a table and cannot contain NULL values?

A. Foreign Key

B. Secondary Key

C. Primary Key

D. Candidate Key

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Correct Answer: Option C

Explanation:
A Primary Key is a unique identifier for each tuple in a relation. It enforces entity integrity and strictly cannot accept NULL values.

This question belongs to: Computer Database Management System (DBMS)

Question #193

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A key that consists of more than one attribute to uniquely identify rows in a table is called a what?

A. Secondary Key

B. Primary Key

C. Composite Key

D. Foreign Key

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Correct Answer: Option C

Explanation:
When a primary key or unique key comprises two or more columns (attributes) combined together, it is known as a Composite Key.

This question belongs to: Computer Database Management System (DBMS)

Question #194

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Which key establishes a logical relationship between two tables by referencing the primary key of another table?

A. Alternate Key

B. Foreign Key

C. Candidate Key

D. Super Key

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Correct Answer: Option B

Explanation:
A Foreign Key is an attribute or collection of attributes in one table that references the primary key of another table to maintain referential integrity.

This question belongs to: Computer Database Management System (DBMS)

Question #195

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Any set of one or more attributes that collectively allow us to uniquely identify tuples in a relation is termed as a what?

A. Super Key

B. Local Key

C. Foreign Key

D. Secondary Key

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Correct Answer: Option A

Explanation:
A Super Key is any set of attributes within a table that can uniquely identify a row. A candidate key is a minimal super key.

This question belongs to: Computer Database Management System (DBMS)

Question #196

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Candidate keys that are not selected or designated as the primary key of a table are known as what?

A. Foreign Keys

B. Super Keys

C. Alternate Keys

D. Composite Keys

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Correct Answer: Option C

Explanation:
Out of all available candidate keys, the one selected to identify rows uniquely is the primary key, and the remaining unselected candidate keys are called alternate keys.

This question belongs to: Computer Database Management System (DBMS)

Question #197

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Which property of a DBMS ensures that all operations within a transaction are completed successfully, or none of them are executed at all?

A. Atomicity

B. Durability

C. Isolation

D. Consistency

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Correct Answer: Option A

Explanation:
Atomicity follows the 'all-or-nothing' rule, ensuring that a transaction is either fully committed or completely rolled back if an error occurs.

This question belongs to: Computer Database Management System (DBMS)

Question #198

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What does the letter 'D' stand for in the widely accepted ACID properties of database transactions?

A. Data

B. Definition

C. Dependency

D. Durability

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Correct Answer: Option D

Explanation:
ACID stands for Atomicity, Consistency, Isolation, and Durability. Durability ensures that once a transaction commits, its changes survive system failures.

This question belongs to: Computer Database Management System (DBMS)

Question #199

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The concept that prevents concurrent transactions from interfering with each other and creating data inconsistencies is known as what?

A. Consistency

B. Durability

C. Isolation

D. Atomicity

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Correct Answer: Option C

Explanation:
Isolation ensures that the execution of concurrent transactions does not interfere with one another, making them appear as if they are executing sequentially.

This question belongs to: Computer Database Management System (DBMS)

Question #200

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Which schema architecture level describes how the data is physically stored on disk storage media?

A. Logical Level

B. External Level

C. Conceptual Level

D. Internal Level

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Correct Answer: Option D

Explanation:
The Internal (or Physical) level of the three-schema architecture describes the physical storage structure and access paths of the database.

This question belongs to: Computer Database Management System (DBMS)

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